The invention relates to a process and an arrangement for picking up a yarn end of a spool package during a piecing operation at a spinning unit which produces packages serving as feeding packages for a subsequent twisting. The spinning unit is part of a spinning machine having a plurality of such spinning units in each of which two slivers are drawn and are subsequently prestrengthened by false-twisting into yarns which are guided together and are wound on the spool package as a double yarn.
In practice, it is difficult to pick up the yarn end of a double yarn at a spool package, particularly if both yarns are not broken simultaneously and are therefore not located at the same point of the spool package. In order to solve this problem, it is provided in an older commonly assigned patent application Ser. No 07/340,708 filed Apr. 20, 1989 now abandoned based on German Application No. 33661 p 38 13 368, which is no prior publication, that in the case of a yarn breakage, the winding-up and the spinning operation is interrupted in such a manner that the unbroken yarn is held in a yarn pick-up position from which it can be picked up by means of a suction gripper during a piecing. During a piecing, only the unbroken yarn is then picked up first and wound off the spool package, this yarn, during the winding-off, taking along the broken yarn off the spool package, so that this yarn end can also be found and can also be withdrawn.
An object of the invention is to improve the picking-up of the yarn end.
This object is achieved in that, in the case of a yarn breakage, the winding-up and the spinning operation are interrupted in such a manner that the unbroken yarn end is held in a yarn pick-up position from which, during the piecing, it is picked u by means of a suction gripper which can be applied to the yarn pick-up position, and in that, after an unsuccessful piecing attempt, the suction gripper is applied to the circumference of the spool package.
This construction takes into account the circumstance that situations exist in which no yarn is available in the yarn pick-up position. The possibility is then opened up to nevertheless pick up the yarn end at the spool package. This type of a situation may occur if, for example, both yarn components break simultaneously or almost simultaneously, so that both yarns are completely wound onto the spool package. In this case, the first attempt must be unsuccessful because no yarn is withdrawn from the spool Package. This situation will also occur when the first piecing attempt was unsuccessful because then a yarn is also no longer available in the yarn pick-up position.
In a further development of certain preferred embodiments of the invention, it is provided that, in the case of a breakage of both yarn components, the suction gripper is applied to the circumference of the spool package for the subsequent piecing attempt. In this case, the circumstance may be taken into account that then a first spinning attempt will not be carried out at all which, because of an absence of a yarn at the yarn pick-up position, must necessarily remain unsuccessful.
In a further development of certain preferred embodiments of the invention, it is provided, in the case of an arrangement for picking up a yarn end of a spool package during piecing, that the devices for monitoring yarn breakage and for interrupting the spinning operation contain a sequence control which first interrupts the winding-up of the remaining yarn and then the spinning operation, that devices are provided for keeping the yarn, which is not yet wound onto the spool package, available in a yarn pick-up position, and that a suction gripper is provided which can be applied to the yarn pick-up position and to the circumference of the spool package. Such a suction gripper can therefore, pick up an individual yarn in two different positions and, if necessary, also a double yarn. In this case, it is provided in an expedient development that the suction gripper has a suction opening which is adapted to the path of the yarn in the yarn pick-up position and to the circumference of the spool package.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.